spi: omap2-mcspi: Revert FIFO support without DMA

spi: omap2-mcspi: Revert FIFO support without DMA

MCSPI controller have few limitations regarding the transaction
size when the FIFO buffer is enabled and the WCNT feature is used
to find the end of word, in this case if WCNT is not a multiple of
the FIFO Almost Empty Level (AEL), then the FIFO empty event is not
generated correctly. In addition to this limitation, few other unknown
sequence of events that causes the FIFO empty status to not reflect the
exact status were found when FIFO is being used without DMA enabled
during extended testing in AM65x platform. Till the exact root cause
is found and fixed, revert the FIFO support without DMA.

See J721E Technical Reference Manual (SPRUI1C), section 12.1.5
for further details: http://www.ti.com/lit/pdf/spruil1

This reverts commit 75223bbea840e ("spi: omap2-mcspi: Add FIFO support
without DMA")

Signed-off-by: Vaishnav Achath <vaishnav.a@ti.com>
Link: https://msgid.link/r/20240212120049.438495-1-vaishnav.a@ti.com
Signed-off-by: Mark Brown <broonie@kernel.org>